niter
>
Niter or nitre is the mineral form of potassium nitrate, KNO₃. It is a soft, white, highly soluble mineral found primarily in arid climates or cave deposits. Wikipedia
Color: White
Crystal class: Dipyramidal (mmm); H-M symbol: (2/m 2/m 2/m)
Crystal habit: Druse or acicular
Crystal system: Orthorhombic
Formula (repeating unit): KNO3
IMA symbol: Nit
Mohs scale hardness: 2